H-T magnetic phase diagrams of electron-doped Sm1-xCaxMnO3:: Evidence for phase separation and metamagnetic transitions -: art. no. 144426

The magnetic properties of the polycrystalline manganites Sm1-xCaxMnO3 have been studied for (1 greater than or equal to x greater than or equal to 2/3) under high magnetic fields up to 50 T. The phase diagrams in the H-T plane have been determined. The more representative systems have also been studied by means of neutron diffraction experiments. Increasing the electron concentration in CaMnO3 leads to an increasing minor ferromagnetic (FM) component superimposed on the antiferromagnetic (AFM) background. A cluster-glass regime is observed for x = 0.9, where FM clusters an embedded in the G-type AFM matrix of the parent compound. For 0.8 greater than or equal to x, field-induced transitions from the AFM ground state to a FM one have been observed. They correspond to the melting of the C-type AFM orbital-ordered phase for x = 0.8, and to the collapse of the charge-ordered phase for x = 3/4. In between these two characteristic domains of concentration, x similar to 0.85, the magnetization curves show a superposition of the two above behaviors, suggesting phase separation. This scenario is consistent with the neutron diffraction results showing that the crystalline and magnetic structures of each phase coexist.